OBSERVATIONS OF BOUNDARY LAYER STRUCTURE FROM AIRCRAFT AND THE

INTERNATIONAL TEAMx PROGRAM

AQUARIUS WORKSHOP 25/26 September 2019, University of UtahSESSION 6 : INSIGHTS FROM OTHER REGIONS

Stephan F.J. De Wekker

University of VirginiaDepartment of Environmental Sciences

Multi-scale flow interactions and boundary layer structure

Synoptic flow

Local scale flows - mesoscale flows - synoptic scale flows

Convergence/divergence, wind shear, turbulence, etc.

Effects on spatial and temporal variability of PBL structure

PBL height

Whiteman, 2000

De Wekker, S.F.J., and M. Kossmann, 2015: Convective boundary layer heights over mountainous terrain: A review of concepts. Front. Earth Sci., DOI: 10.3389/feart.2015.00077

potential temperature horizontal wind

2 km

2 km

TRACT – Rhine Valley - Black Forest, Germany, Kossmann et al. 199850 km

1 km

‘simple’ cross-valley and along valley flight legs

MAP – Riviera Valley, Switzerland, De Wekker et al. 2004

BOUNDARY LAYER STRUCTURE FROM AIRCRAFT

In-situ measurements

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Lack of observations over ridges and slopes

De Wekker et al. 2002

BOUNDARY LAYER STRUCTURE FROM AIRCRAFT In-situ measurements of turbulence kinetic energy

DLR Falcon

BOUNDARY LAYER STRUCTURE FROM AIRCRAFTRemote sensing measurements

downlooking aerosol lidar

De Wekker 2002, 2015

Multi-layer-structureSpatial heterogeneitiesPBL height vs. aerosol layer height

Henne et al., 2004

DLR Falcon

BOUNDARY LAYER STRUCTURE FROM AIRCRAFTRemote sensing measurements

1500 m

0 m

Accelerating valley flow-> sinking motions

Salinas Valley, CA, De Wekker et al., 2012~ 40 km

Accumulation of aerosols eastern part of valley

downlooking Doppler lidar

Navy Twin Otter

The UWOW can collect measurements at stationary fixed location AND as it travels along the roads and highways.

BOUNDARY LAYER STRUCTURE FROM GROUND VEHICLE (UVA – Wind Observatory on Wheels- UWOW)

Wind profiles from about 100 m to ~3000 m or more (depending on atmospheric conditions and lidarsettings) at ~1 km horizontal spacing and 30 m vertical spacing.

Great opportunities to merge with mobile chemistry labs!

When focus is on investigating boundary layer structure, experimental design for airborne observations often relatively simple and straightforward

What happens if the project becomes multi-disciplinary?

Example: Airborne Carbon in the Mountains Experiment (ACME) 2004, 2007. Major objective: estimating CO2 budget in the Colorado Rocky Mountains: experimental strategy focused on following airmasses

Sun et al., 2010

300 km

300 km

Conflicting thoughts about optimal experimental design. Large challenges in attempting to ‘measure it all’

MULTI-DISCIPLINARY AIRCRAFT MISSIONS~flight tracks of ~15 flight missions

Quite chaotic flight patternsevery mission is unique

Morning Mountain Valley CO2 ProfilesMorning flight path afternoon flight path

MULTI-DISCIPLINARY AIRCRAFT MISSIONS

De Wekker et al., 2006; Sun et al., 2010

incomplete observations of boundary layer structure make it difficult to quantify uncertainties in applying boundary layer budget method for estimating CO2 fluxes

Steering committee:

Mathias W. Rotach1, Marco Arpagaus2, Joan Cuxart3, Stephan De Wekker4, Vanda Grubišić5, Norbert Kalthoff6, Dan Kirshbaum7, Manuela Lehner1, Stephen Mobbs8, Alexandre Paci9, Elisa Palazzi10, Stefano Serafin1, Dino Zardi11

1University of Innsbruck, 2MeteoSwiss, 3University of the Balearic Islands4University of Virginia, 5NCAR EOL, 6Karlsruhe Institute of Technology, 7McGill University 8National Centre of Atmospheric Sciences, 9Meteo France, 10ISAC CNR, 11University of Trento

Multi-scale Transport andExchange Processes in theAtmosphere over Mountains

Programme and experiment

TEAMx is an international research program with the general aim to measure exchange processes in the atmosphere over mountains and to evaluate how well these are parameterized in NWP and climate models.

First TEAMx workshop 28-30 August 2019, Rovereto (Italy)

TEAMx Memorandum of Understanding between the institutions of the CIG members. Signed by 9 institutions (U. Innsbruck, Meteo Swiss, Meteo France, U. Virginia, McGill U, U. Trento, C2SM, NCAS, KIT. Open to new partners

Publication of 9 review articles in special issue “Atmospheric Processes over Complex Terrain” (editors M. Rotach and D. Zardi) in journal “Atmosphere”

White paper. Draft available. To be finalized soonwww.teamx-programme.org

https://www.mdpi.com/journal/atmosphere/special_issues/Complex_Terrain

Workshop topics (addressed in White Paper)

Mountain Boundary Layer Flows Land atmosphere exchange Orographic convection Orographic flow dynamicsAir chemistry and atmospheric dispersion modellingClimate processes / climate change in mountains

Strategy for field experimentStrategy for numerical modelling

Some examples of research questions

• What processes contribute to daytime/nighttime exchange in the mountain boundary layer? How can the “overall exchange” be quantified?

• What vertical and horizontal length scales are most relevant for mountain BL exchange? How do we define the mountain BL height?

• Do current models account for exchange processes in the mountain BL?

• Is subgrid-scale parameterization of mountain-induced exchange of heat and mass necessary for O(10 km) grid-spacing models? (e.g., similar to orographic drag)

Field experiment

• Planned for 2023 • In the European Alps• various ‘super sites’ addressing multi-scale processes• One of the supersites near Innsbruck, Austria – “i-Box” (network of surface flux

stations) • Request of UK and German research aircraft planned• US efforts are planned (e.g. request of aircraft, ground-based observing facilities,

SPO, EDO) - air chemistry component currently not well developed• Scoping meeting on Wednesday 9 October at NCAR (after UCAR meeting), 5 – 7

PM MT (remote participation possible)

Please contact Stephan de Wekker dewekker@Virginia.edu